String - Revision history

Wervyn: touchup

2008-06-13T13:00:38Z

touchup

Wervyn: Done for now

2008-06-13T07:03:19Z

Done for now

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 The term "'''string'''" in [[MegaZeux]] is now most commonly used to refer to string variables, introduced in a limited capacity in version 2.62.  MZX also refers to any value enclosed in quotes (<tt>"</tt>) in [[Robotic]] code as a string, with interpretation dependent on context.  However, this meaning is so trivial and general that it would be more productively explored in specific articles on Robotic functionality.
 ==Basic String Syntax==
-String variables (henceforth referred to as "strings" for brevity) work in much the same way as counters, in terms of where and how they can be used in Robotic.  Any counter name prefixed with a dollar sign (<tt>$</tt>) is interpreted as a string.  Like counters, strings can be assigned to with set, [[counter interpolation|interpolated]] with ampersands (<tt>&</tt>), compared with an if branch (limited to equality and inequality), and read and written to and from files.  Strings can also be concatenated using the inc command.
+String variables (henceforth referred to as "strings" for brevity) work in much the same way as counters, in terms of where and how they can be used in Robotic.  Any counter name prefixed with a dollar sign (<tt>$</tt>) is interpreted as a string.  Like counters, strings can be assigned to with set, [[counter interpolation|interpolated]] with ampersands (<tt>&</tt>), compared with an if branch (less-than and greater-than are quirky, however), and read and written to and from files.  Strings can also be concatenated using the inc command.
 The value assigned to a string depends on context:
   set "$string" to 42            ''sets a string to the text "42", from a literal value''
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   set "$string" to "board_name"  ''sets a string to the name of the current board''
 As you can see, there are three basic cases and some special considerations.  First, a string set to a numeric literal becomes a string representation of that number.  Second, a string set to a STRING literal becomes (in most cases), that literal, NOT a counter named by that literal.  In order to set a string to the value of a numeric counter, that counter must be interpolated into the string literal.  Finally, a string can be set to another string (i.e. when the second value also begins with $).  However, in addition to these general cases, there are also some special keywords interpreted as built-in string values instead of literals.  Currently, these include "fread" and "fwrite", and both of these followed by a number value, for [[file access]]; "robot_name", "board_name", and "mod_name", which return the name of the currently executing robot, the current board, and the currently playing module music file; and "INPUT", which is itself interpreted as a string, and is the value returned from an "input string "Prompt"" command.  In order to actually set a string to these literal values (or a literal string beginning with $ for that matter), it must be specially constructed using other commands.

Wervyn: In progress.

2008-06-12T20:41:03Z

In progress.

New page

The term "'''string'''" in [[MegaZeux]] is now most commonly used to refer to string variables, introduced in a limited capacity in version 2.62. MZX also refers to any value enclosed in quotes (<tt>"</tt>) in [[Robotic]] code as a string, with interpretation dependent on context. However, this meaning is so trivial and general that it would be more productively explored in specific articles on Robotic functionality.
==Basic String Syntax==
String variables (henceforth referred to as "strings" for brevity) work in much the same way as counters, in terms of where and how they can be used in Robotic. Any counter name prefixed with a dollar sign (<tt>$</tt>) is interpreted as a string. Like counters, strings can be assigned to with set, [[counter interpolation|interpolated]] with ampersands (<tt>&</tt>), compared with an if branch (limited to equality and inequality), and read and written to and from files. Strings can also be concatenated using the inc command.
The value assigned to a string depends on context:
set "$string" to 42 ''sets a string to the text "42", from a literal value''
set "$string" to "42" ''sets a string to the text "42", from a literal string value''
set "$string" to "counter" ''sets a string to the text "counter", a literal string value''
set "$string" to "&counter&" ''sets a string to the value of the counter "counter", via interpolation''
set "$string" to "$string2" ''sets a string to the value of another string, "$string2".''
set "$string" to "fread" ''sets a string to a value read from a [[file access|file]], terminated by an asterisk (*)''
set "$string" to "fwrite" ''does NOT set, but WRITES a string to a file, terminating it with an asterisk (*)''
set "$string" to "board_name" ''sets a string to the name of the current board''
As you can see, there are three basic cases and some special considerations. First, a string set to a numeric literal becomes a string representation of that number. Second, a string set to a STRING literal becomes (in most cases), that literal, NOT a counter named by that literal. In order to set a string to the value of a numeric counter, that counter must be interpolated into the string literal. Finally, a string can be set to another string (i.e. when the second value also begins with $). However, in addition to these general cases, there are also some special keywords interpreted as built-in string values instead of literals. Currently, these include "fread" and "fwrite", and both of these followed by a number value, for [[file access]]; "robot_name", "board_name", and "mod_name", which return the name of the currently executing robot, the current board, and the currently playing module music file; and "INPUT", which is itself interpreted as a string, and is the value returned from an "input string "Prompt"" command. In order to actually set a string to these literal values (or a literal string beginning with $ for that matter), it must be specially constructed using other commands.

← Older revision		Revision as of 13:00, 13 June 2008
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	As with setting, strings can be compared to string or number literals as well. In this case, the variable string must be the first value, like so:		As with setting, strings can be compared to string or number literals as well. In this case, the variable string must be the first value, like so:
	if "$string1" < "test" then "STRING" ''performs a less-than comparison based on the value of $string1 and "test"''		if "$string1" < "test" then "STRING" ''performs a less-than comparison based on the value of $string1 and "test"''
	if "test" > "$string1" then "NUMBER" ''performs a greater-than comparison based on the value of the counter "test" and the numeric value of $string1		if "test" > "$string1" then "NUMBER" ''performs a greater-than comparison based on the value of the counter "test"''
			''and the numeric value of $string1''
	if "$string1" = 42 then "MATCH" ''compares the equality of $string1 with the string representation of 42''		if "$string1" = 42 then "MATCH" ''compares the equality of $string1 with the string representation of 42''
	if 42 = "$string1" then "MATCHAGAIN" ''compares the equality of the number 42 with the numeric representation of $string1''		if 42 = "$string1" then "MATCHAGAIN" ''compares the equality of the number 42 with the numeric representation of $string1''
	The last two comparisons actually accomplish the same thing, but in notably different ways.		The last two comparisons actually accomplish the same thing, but in notably different ways.

	Finally, strings can be interpolated using ampersands, just like any other counter. Attempting to do this with [[expressions\|~~expressions~~]] syntax, however, will numerically evaluate the string instead of include its string value. So for instance:		Finally, strings can be interpolated using ampersands, just like any other counter. Attempting to do this with [[expressions\|expression]] syntax, however, will numerically evaluate the string instead of include its string value. So for instance:
	* "~F&$string&" ''displays the value of $string''		* "~F&$string&" ''displays the value of $string''
	* "~F('$string')" ''displays the numeric evaluation of $string''		* "~F('$string')" ''displays the numeric evaluation of $string''
	An interesting note about this, is that in places where the string is interpolated into a value that understands ~ and @ color codes, those codes can be included in the string as well. This really shouldn't be surprising at all, but it is worth pointing out.		An interesting note about this, is that in places where the string is interpolated into a value that understands ~ and @ color codes, those codes can be included in the string as well. This really shouldn't be surprising at all, but it is worth pointing out. Also, while things like "robot_name" are special keyword hacks for the set command only, "INPUT" has been in MZX since before any other strings were, and can be interpolated just fine.

	==Advanced String Syntax==		==Advanced String Syntax==
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	set "$string" to "$string.5" ''sets the string to the numeric value of its 5th character''		set "$string" to "$string.5" ''sets the string to the numeric value of its 5th character''
	set "$string+5" to "blah" ''replaces the end of the string (after 5 characters) with "blah"''		set "$string+5" to "blah" ''replaces the end of the string (after 5 characters) with "blah"''
	set "$string#5" to "lots of text" ''replaces the string with the first 5 characters of "lots of text" (probably a bug)''		set "$string#5" to "lots of text" ''replaces the string with the first 5 characters of "lots of text"''
	set "$string+0#5" to "lots of text' ''same as previous (almost certainly a bug)''		''(probably a bug)''
	set "$string+5#5" to "lots of text' ''replaces a substring in the string with the first 5 characters of "lots of text" (intended behavior)''		set "$string+0#5" to "lots of text" ''same as previous (almost certainly a bug)''
			set "$string+5#5" to "lots of text" ''replaces a substring in the string with the first 5 characters of
			''"lots of text" (intended behavior)''
	set "$string+&$string.length&" to "append" ''appends "append" to the end of the string''		set "$string+&$string.length&" to "append" ''appends "append" to the end of the string''
	The last example demonstrates on final feature of strings: the special value "$string.length" is, as one might expect, the length of the string. This value is supposed to be read-only, but currently assigning a value to it seems to interpret it as "$str.0", and assigns a new value to the first character of the string.		The last example demonstrates on final feature of strings: the special value "$string.length" is, as one might expect, the length of the string. This value is supposed to be read-only, but currently assigning a value to it seems to interpret it as "$str.0", and assigns a new value to the first character of the string.

	[[Category:MegaZeux]]		[[Category:MegaZeux]]